1. Field of Invention
This invention relates to a pressure gauge, and more particularly to one which shows a measured pressure in digital numbers.
2. Description of the Related Art
Referring to FIG. 1, a Bourdon pressure gauge (1) is shown to comprise a C-shaped pipe (11) of an oval cross-section (see in FIG. 3) through which a pressurized fluid from a fluid inlet (10) can flow. When the pressure inside the pipe (11) is increased, the C-shaped pipe (11) tends to straighten, causing the pipe (11) to straighten, as shown in FIG. 2. The sealed inner end portion (110) of the pipe (11) will impel an end of a connecting rod (121). The other end (124) of the connecting rod (121) in turn rotates a sector gear (122) about a pivot pin (125) so that an indicating needle (102) is rotated by meshing the teeth (123) of the sector gear (122) with a gear (103) of the indicating needle (102). Since the upper casing of the Bourbon pressure gauge has a marking scale (104), the needle (102) will point to the corresponding mark in response to the applied weight.
A drawback of the above-mentioned pressure gauge is that when the indicating needle (102) lies between two marks of the scale, one can not tell the precise weight of an object. When measuring an object, the value of which must be known precisely, such pressure gauge is not desirable.